That’s not implemented, but you can click the maximize button, or press Super+M to toggle maximization.
You can open the Appearance settings page and change that to your preferred color scheme. We’ve already selected our default colors and they’re not going to change from here on out.
What do you mean by minimal? The PrintScrn key opens the screenshot utility, which lets you choose between capturing a selected region, a specific window, or the whole display
What’s wrong with the file manager and editor? You can use whatever editor and file manager you want, so that shouldn’t be a blocker for daily use.
This can be configured in the cosmic comp config, but will be implemented in the settings app soon.
Super+W opens the workspaces view
Your distribution should make sure pop-launcher is installed, and each of its plugins symlinked.
That is already possible in the Desktop and Panel settings page. As you can see, I’m not using a GNOME style panel or dock here.